This invention is concerned with boring bars for metalworking. In metalworking, especially when forming internal diameters in workpieces, it is desirable to use what is known as a compensating boring bar. Compensating boring bars have cutting inserts mounted around the periphery of the working end of the bar.
The cutting inserts are seated on tool units that are capable of some radial adjustment relative to the boring bar. The range of radial adjustment need not be great, but should be enough to allow the boring bar to be removed from a finish cut without marking the workpiece. In order to accomplish this adjustment, mechanisms are provided so that the tool units and cutting inserts can be adjusted radially inward so as to provide clearance between the finish bore size and the cutting diameter of the inserts. When this is accomplished, usually after the finish cut has been made, the tool unit can safely be removed from the workpiece.
Previous boring bars with adjustment mechanisms have utilized cone-shaped ramps to adjust the tool units radially and have also used constant diameter plug members in combination with the cone-shaped ramps.
Many problems are encountered when utilizing the previously known boring bars in that the cone-shaped ramps make only a single point contact with the tool units and allow the tool units to shift positions during cutting operations. Further, the constant diameter spacers used previously allowed the various mechanism tolerances of the individual parts of the bar to add up and affect the overall tolerances on the position of the cutting inserts.
Both the shifting of the inserts and the tolerance build-up on the positioning of the inserts are undesirable features when attempting to make very precise finish cuts in workpieces.
The number of tool units on the bar can be one, or more, depending upon one's preference.